relocating drain in a slab floor - concerned about floor

We want to relocate our washer/dryer about 10 ft from its original location. We have a slab floor, so re-routing the drain would mean digging a trench in the slab floor to run the new drain pipe.

My concern is the cutting up the slab floor part - all the plumbers I've talked to have no issue with it, but I'm concerned for my foundation. Would cutting into the slab affect the foundation? The house is ~ 35-40 yrs old - and so far the foundation & slab are in great condition.

Normally not a problem. But, if your house is built using a post-tensioned slab...big problems. Post-tensioned slabs have steel cables embedded in them that are terminated in a threaded connection and they are tightened after the slab is poured. They help in earthquake country and on less than ideal soil conditions to keep things from cracking. Cutting through one of those cables can be very dangerous.

The least amount of damage would be a wet saw contractor. They use a diamond blade cooled with a stream of water so there is no dust.
Since the slab is cut and not hammered, it stays more intact. Also pouring new concrete back is easier.

If you go "old school" and use a jackhammer, turn off the forced air heat.
When those things kick on it can spread concrete dust all over the house.

I agree with using a wet saw. The water is still a bit messy, but will control the dust. I dry cut my slab with a diamond blade, but the dust goes everywhere. It gets so bad, that you have to stop often as the dust is so thick, you can't see what you are doing (covers the goggles too). I made sure that the HVAC was off and tried to close off the area to the rest of the house and open windows to let the dust escape, but dust still went everywhere. Even the 2nd floor (with the slab being cut in the basement) saw significant dust.

You can save some $$ doing it yourself, but prepared to be cleaning everything in your house for some time.